Impedance matching device for wave guides for antenna systems



. R. we. ROBERTSON I IMPEDANCE MATCHING DEVICE FOR WAVE.

s pg '12, 1950 2,521,873

GUIDES FOR ANTENNA SYSTEMS I Filed Oct. 30, 1944" A\\\\\\\\\\\\ IIIIIIIIIIII;

INVENTOR- RANDAL M66. ROBERTSON BY I ,qffakrrey Patented Sept. 12, 1950 'sai IMPEDANCE tary of War ApplicationQctober 30 """sclaims. (pens on This invention relates to directive antenna systems for transmission and reception of high frequency radio waves, and more particularly to antenna arrays using a variable-width wave guide.

, The present invention is directed to an arrangement for maintaining a desirable degree of power transfer between a wave guide of fixed width and a wave guide of variable width. This device depends upon the discovery that a satisfactory impedance match can be maintained provided that the wave guide of fixed width is moved so that it remains centered with respect to the wave guide of variable width. The invention will more readily be understood from the following description with reference to the accompanying drawings in which:

Fig. 1 is a back elevation view partly broken off of an arrangement according to this invention for matching a scanning antenna to a wave guide leading to a transmitting and receiving system; and

Fig. 2 is an enlarged cross-sectional view of the same along the line 2-2 of Fig. 1.

Referring to the drawings, a lower narrow wall member 6 of wave guide 5 is fixed in position upon .a fixed front plate III which carries an array of dipoles (not shown). An upper narrow wall member I of wave guide 5 reciprocates in a vertical direction, as driven by the scanning mechanism (not shown), and is carried by a movable back plate II. A rack I2 (Fig. 2) is mounted on plate II and another rack I 3 is mounted upon a bracket I4 which is carried on the front plate l near one of its longitudinal extremities. A pinion, or preferably a pair of pinions I5 and I6 are arranged between and are adapted to engage racks I2 and I3 and are mounted in a small frame ll. It will be seen that the movement of the rack I2 as a result of the scanning motion impressed upon the back plate II will impress upon the frame I! a motion having half the amplitude of the driving motion. This motion is then impressed upon the fixed-width wave guide I8 by means of an arm I9, projecting from the frame H, which is fastened to the wave guide l8 by means of a pivot connection. The arm I9 is preferably in the formof a bar or tongue adapted to fit into a groove or slot 20 located substantially mid-way of the width of the frame I! and desirably between the pinions l5 and I6. It will be obvious, however, that the exact location and manner of mounting of the arm 19 on the frame need not be limited to this. particu-- lar structure.

The wave guide l8, shown broken away at 2| MATonINGnEvrcE F-onw GUIDESFQR ANTENNASfiZSTEMS Y .tl .,a ana M elgnb rtsortjjca, marinas; as )s'ignor, by inesne assignments, tqgth States of America as r' represented by l th I i344, ser l.- N

to simplify the illustration, may be folded back on itself and, at a suitable place in the portion of the wave guide thus folded in back of the antenna array, a wobble joint or other suitable connection is provided in a well-known manner in order to permit the wave guide I8 to follow the motion impressed upon it by the frame I'I. Because the motion of the frame I! has exactly half the amplitude of the motion of back plate II, the frame I1, after proper setting, will automatically maintain the fixed-width wave guide I8 centered with respect to the variable-width wave guide 5 which feeds the antenna array.

If desired, a suitable coupling member 22 may be mounted in known manner on the end of the fixed-width wave guide I8 and the arm I9 may be pivotally connected to the coupling member so that the movement of the arm I9 will be impressed on the coupling member 22 and the wave guide I8.

While a preferred embodiment of the present invention has been illustratedand described, it will be understood this is capable of modification and improvement without departing from the spirit of the invention. Therefore it is not desired that the scope of the invention be limited to the precise details set forth.-

What is claimed is:

1. A wave guide system comprising a wave guide of fixed width, a variable width wave guide having a fixed sidewall and an opposite movable side wall, and means for maintaining the fixedwidth and variable-width wave guides mutually centered comprising a rack member rigidly associated with said fixedside wall, a second rack member rigidly associated with said movable side wall, pinion means located between said racks and engageable therewith, and means connecting said pinion means and said fixed-width wave guide, a movement of said second rack member causing movement of said pinion means and of said fixed-width wave guide in the same direction but of half the amplitude of movement of said movable side wall, thus maintaining the fixed-width and variable width wave guides mua 3 said one member and said fixed width wave guide and responsive to said displacement to move said fixed width wave guide with respect to said other member in the same direction and through half lithe distance of said displacement of said one member for maintaining said fixed and said variable widths. wave" 'ifiguides mutually centered wherebya satisfactory impedancematch is obtained. "3. A wave guide arrangement for impedance fixed width wave guide andtino'ludingfafixedfwall and a movable wall, means'lfoiii-fisl aiin said.

movable wall to vary a dimension of said variable 'width wave guide, and mechanical linkage means coupling said fixed width waveguide sass-id movable wall and responsive to the displacement of matching a fixed width waveisuideztcrrawariable o width wave guide comprising aZfixedmiidthWave guide, a variable width wave guide .coupledto said said movable wall to displace said fixed width wave guide in the same direction through half the distance of said displacement of said movable wall to maintain said fixed width and variable width wave guides mutually centered.

x ROBERTSON.

EEFERENESCITED The following references are of record in the file of this patent:

Z'iJiIHNITED STATES PATENTS Number Name Date *---"'23i83-,'368 Johnson Dec. 30, 1947 .[234580308 Alvarez Aug. 30, 1949 "FOREIGN PATENTS ir-i ---l l nmber v dzfiountry Date 503,467 Great Britain Apr. 6, 1939 

